Platelet hyperaggregability in high-fat fed rats: a role for intraplatelet reactive-oxygen species production

Abstract

Background: Adiposity greatly increases the risk of atherothrombotic events, a pathological condition where a chronic state of oxidative stress is reported to play a major role. This study aimed to investigate the involvement of (NO)-soluble guanylyl cyclase (sGC) signaling pathway in the platelet dysfunction from high fat-fed (HFF) rats.

Methods: Male Wistar rats were fed for 10 weeks with standard chow (SCD) or high-fat diet (HFD). ADP (10 μM)- and thrombin (100 mU/ml)-induced washed platelet aggregation were evaluated. Measurement of intracellular levels of ROS levels was carried out using flow cytometry. Cyclic GMP levels were evaluated using ELISA kits.

Results: High-fat fed rats exhibited significant increases in body weight, epididymal fat, fasting glucose levels and glucose intolerance compared with SCD group. Platelet aggregation induced by ADP (n = 8) and thrombin from HFD rats (n = 8) were significantly greater (P < 0.05) compared with SCD group. Platelet activation with ADP increased by 54% the intraplatelet ROS production in HFD group, as measured by flow cytometry (n = 6). N-acetylcysteine (NAC; 1 mM) and PEG-catalase (1000 U/ml) fully prevented the increased ROS production and platelet hyperaggregability in HFD group. The NO donors sodium nitroprusside (SNP; 10 μM) and SNAP (10 μM), as well as the NO-independent soluble guanylyl cyclase stimulator BAY 41-2272 (10 μM) inhibited the platelet aggregation in HFD group with lower efficacy (P < 0.05) compared with SCD group. The cGMP levels in response to these agents were also markedly lower in HFD group (P < 0.05). The prostacyclin analogue iloprost (1 μM) reduced platelet aggregation in HFD and SCD rats in a similar fashion (n = 4).

Conclusions: Metabolic abnormalities as consequence of HFD cause platelet hyperaggregability involving enhanced intraplatelet ROS production and decreased NO bioavailability that appear to be accompanied by potential defects in the prosthetic haem group of soluble guanylyl cyclase.

Figure 1

Effect of 10-week high-fat diet (HFD) or standard chow diet (SCD) on oral glucose tolerance test (OGTT; panel A) and insulin tolerant test (ITT; panel B). The values represent means ± SEM for n = 4-6 rats each group. * p <0.05 compared with control group.

Figure 2

Effect of high-fat diet in the generation of intraplatelet reactive-oxygen species (ROS). Male Wistar rats were fed with either a standard chow diet (SCD) or high-fat diet (HFD) during 10 weeks. Washed platelets (1.2 × 10⁸ platelets/ml) from SCD or HFF rats were pre-incubated with N-acetylcysteine (NAC, 1 mM for 15 min) or PEG-catalase (1000 mU/ml, 15 min) and then stimulated with ADP (10 μM). Generation of ROS was quantified by flow cytometry using 2'-7'-dichloroflurescin diacetate (DCFH-DA). Results are shown as mean ± SEM values for n = 6-7. *P < 0.05 compared with SCD group. ^#P < 0.05 compared with ADP in HFF group. MFI = mean fluorescence index.

Figure 3

Effect of N-Acetylcysteine (NAC) and PEG-catalase on washed platelet aggregation of rats fed with a standard chow diet (SCD) or high-fat diet (HFD) during 10 weeks. Washed platelets (1.2 × 10⁸ platelets/ml) from SCD or HFD rats were stimulated with thrombin (100 mU/ml; panel A) or ADP (10 μM; panel B) in the absence or the presence of NAC (1 mM) or PEG-catalase (1000 U/ml). Results are shown as mean ± SEM values (n = 4-7). *P < 0.05 compared with untreated control group. ^#P < 0.05 compared with the respective untreated platelets.

Figure 4

Effect of sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine (SNAP) and BAY 41-2272 on washed platelet aggregation (panel A) and cyclic GMP production (panel B) in rats fed with a standard chow diet (SCD) or high-fat diet (HFD) during 10 weeks. Washed platelets (1.2 × 10⁸ platelets/ml) from SCD or HFD rats were stimulated with ADP (10 μM) in the absence or the presence of SNP, SNAP or BAY 41-2272 (10 μM each). Results are shown as mean ± SEM values (n = 4-7). *P < 0.05 compared with untreated control group. ^#P < 0.05 compared with the respective agent in control group.